Combine flour, oregano, parsley, salt, and garlic powder; coat short ribs with mixture by dredging or shaking in a food storage bag. Discard any remaining flour mixture.
In a skillet over medium heat, brown short ribs on all sides in hot oil. Drain well and place in slow cooker. Add chopped onions, carrots (if using), stock, and beer.
Cover and cook on low heat for 8 to 10 hours or on high for 5 to 6 hours.
Serve with the juices or make a gravy (below).
Notes
To make gravy, skim off the fat, transfer the juices to a saucepan, and cook over medium heat until the liquids are reduced and the flavors are concentrated. Combine 2 tablespoons of flour with 3 tablespoons of cold water and stir until smooth. Add to the juices and cook, stirring, until thickened.